To classify images into meaningful categories is a challenging and important problem in content-based image retrieval. In many methods, a lot of features extracted from whole image are used directly for image classification. As we know, the meaningful features mainly appear in part of an image, not whole image.
“On image classification: city images vs. landscapes” by Aditya Vailaya et al, Pattern Recognition 31(12): 1921-1935 (1998) discussed content-based image classification. The discussion is based on each whole image.